The invention relates to improvements in machines for the making of rod-like fillers containing fragments of tobacco and/or other smokable material. More particularly, the invention relates to improvements in apparatus for evacuating surplus air from a chamber in a distributor (also called hopper) of a machine for the making of plain cigarettes, cigars, cigarillos or other rod-shaped smokable articles of the tobacco processing industry.
Surplus air evacuating apparatus of the character to which the present invention pertains are often utilized in a chamber wherein a flow of fragments of smokable material is conveyed in a stream of gaseous fluid (normally air an hereinafter referred to as air for short) and which is bounded at least in part by a concave surface of a guide. The flow is caused to advance along the concave surface of the guide in a direction from the location where the flow (in an air stream) enters the chamber to a location where the flow leaves the chamber in order to be converted into one or more rod-like fillers ready to be drapped into one or more webs of cigarette paper or other suitable wrapping material. It is often necessary to accelerate the flow of fragmentized smokable material by causing the flow to advance with at least one stream of compressed air. Such stream is or can be circulated along an at least partially closed path, and the surplus of air must be evacuated from such quasi closed path. It is particularly important to regulate the quantity of air in a tobacco conveying system which operates primarily, predominantly or exclusively with compressed air or by suction. Typical examples of such conveying systems are those utilized in the so-called fluidized bed distributors or hoppers of cigarette rod making machines wherein one or more flows of fragments of smokable material are caused to advance along the concave surface of a guide and wherein such surface is provided with orifices for jets or streamlets of compressed air flowing in the general direction of desired transport of fragments of smokable material.
Commonly owned U.S. Pat. No. 5,148,816 granted Sep. 22, 1992 to Heitmann for "Method of and apparatus for making a tobacco stream with a core containing tobacco ribs" discloses a distributor or hopper wherein the upper portion of the wall bounding the chamber for transport of a flow of tobacco particles is perforated to permit the escape of surplus air.
Commonly owned U.S. Pat. No. 4,463,768 granted Aug. 7, 1984 to Quarella for "Apparatus for forming a tobacco filler" discloses a distributor wherein the surplus of air is evacuated through radial bores or holes provided in a rotary drum-shaped conveyor.